Many internal combustion engines now utilize one or more fuel injectors to deliver fuel for combustion. The time of the fuel delivery and the duration of fuel delivery by the fuel injectors are carefully controlled in order to achieve particular engine performance characteristics.
FIG. 1 illustrates an internal combustion engine E in accordance with the prior art. This engine E might be used, for example, to power an automobile or other vehicle.
Regardless of the type of engine E, the engine includes one or more combustion chambers. Fuel and air are provided to the one or more combustion chambers for combustion. Preferably, the fuel is delivered by one or more fuel injectors I. Fuel may be delivered by the one or more injectors I directly to each combustion chamber (“direct” injection) or to an air stream which is provided to each combustion chamber (“indirect” injection). As illustrated, there are four injectors I which are configured to deliver fuel directly to each of four combustion chambers.
Fuel is provided to each injector through a supply line FS, such as from a fuel tank T. Each fuel injector I is controlled by an engine control unit (ECU). The ECU generates control signals which are used to cause each injector I to deliver fuel at a particular time and for a particular duration. The fuel injectors I may be of a variety of types. In one embodiment, the fuel injectors I are energized when an appropriate “ground” signal is transmitted from the ECU which completes an energizing circuit. When the circuit including the fuel injector is energized, the fuel injector opens, allowing pressurized fuel to be delivered to the combustion chamber.
The ECU is programmed to implement a fuel injector control strategy. For example, the control strategy may be configured to optimize engine fuel efficiency. As indicated above, various combinations of injection timing and duration may be employed to achieve a particular performance characteristic for the engine.
One problem with this engine control configuration is that the fuel injection control strategy is fixed. In particular, the ECU is pre-programmed or includes a pre-configured fuel injector control “map.” This pre-programmed control scheme is designed to implement a particular engine control strategy based upon one or more engine characteristics or factors. For example, the pre-programming is performed on the assumption that a particular fuel will be used with the engine, and based upon various engine operating parameters such as throttle position, system voltage, intake plenum air pressure, and engine speed, and may be optimized for a particular engine performance characteristic such as performance or fuel economy.
Such a pre-programmed fuel injector control strategy, however, has drawbacks. First, the strategy or scheme may not result in engine performance characteristics which match those of the user. For example, a user who uses their vehicle for towing rather than running city errands may desire to obtain maximum performance from the engine rather than maximum fuel efficiency.
In addition, the pre-programmed fuel injector control strategy does not account for variations in other external factors. For example, most motor vehicle manufacturers have developed their fuel injector control maps or control schemes based upon the assumption that the user will supply commercially available gasoline to the engine. However, motor vehicle operators have recently been offered the opportunity to use alternative fuels. One such fuel is E-85. This fuel comprises 85% ethanol and 15% gasoline.
As a result of the introduction of these other fuels, automobile manufacturers have realized that the fuel injection control strategy for an engine may need to be modified based upon the fuel which a user supplies to the engine. It is recognized that E-85 provides significantly less energy per volume of fuel than does gasoline. As such, in order to maintain the same engine operating condition, the fuel injection control strategy must be changed to increase fuel injection duration when E-85 fuel is used as compared to when regular gasoline is utilized. A further problem is introduced when considering that the vehicle operator may mix the fuels, such that the fuel which is being drawn from the tank is not E-85 or regular gasoline, but a mixture thereof.
The automobile manufacturer's solution to this problem is illustrated in FIG. 1. As illustrated, the ECU obtains information regarding the fuel which is being supplied to the engine E by a fuel tank sensor FTS. The fuel tank sensor FTS provides a signal to the ECU indicative of the nature of fuel in the tank. The ECU is pre-programmed with fuel injector control maps or schemes which account for variations in the composition of the fuel which is being provided to the engine, as indicated by the fuel tank sensor FTS.
This configuration, however, is expensive and requires that the ECU be pre-programmed “from the factory” by the manufacturer and requires the special fuel tank sensor. However, there are millions of vehicles already in use which do not include a fuel tank sensor and which do not have an ECU which is pre-programmed or mapped with fuel injector control schemes which are dependent upon differences in fuel which is supplied to the engine by the user. In such situations, either the user can not utilize alternative fuels, or if the user does use alternative fuels, the engine will not operate properly.